Most of the great 2D platformers of the 8/16 bit era had quite a great deal of challenge to them. Look back on the Donkey Kong Country series for example, there were many levels that were quite demanding.

All the widely successful 2D platformer throwbacks that have come out the past 4-5 years have one common trait: They all are pretty dang challenging. Whether it's Super Meat Boy or Dead Cells or Donkey Kong Country Returns or Hollow Knight, etc.

In order for these games to properly capture the spirit of the golden age of platformers, it NEEDS CHALLENGE.